--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/lcms2/src/cmssamp.c	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,556 @@
+//---------------------------------------------------------------------------------
+//
+//  Little Color Management System
+//  Copyright (c) 1998-2023 Marti Maria Saguer
+//
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the Software
+// is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
+// THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+//---------------------------------------------------------------------------------
+//
+
+#include "lcms2_internal.h"
+
+
+#define cmsmin(a, b) (((a) < (b)) ? (a) : (b))
+#define cmsmax(a, b) (((a) > (b)) ? (a) : (b))
+
+// This file contains routines for resampling and LUT optimization, black point detection
+// and black preservation.
+
+// Black point detection -------------------------------------------------------------------------
+
+
+// PCS -> PCS round trip transform, always uses relative intent on the device -> pcs
+static
+cmsHTRANSFORM CreateRoundtripXForm(cmsContext ContextID, cmsHPROFILE hProfile, cmsUInt32Number nIntent)
+{
+    cmsHPROFILE hLab = cmsCreateLab4Profile(ContextID, NULL);
+    cmsHTRANSFORM xform;
+    cmsBool BPC[4] = { FALSE, FALSE, FALSE, FALSE };
+    cmsFloat64Number States[4] = { 1.0, 1.0, 1.0, 1.0 };
+    cmsHPROFILE hProfiles[4];
+    cmsUInt32Number Intents[4];
+
+    hProfiles[0] = hLab; hProfiles[1] = hProfile; hProfiles[2] = hProfile; hProfiles[3] = hLab;
+    Intents[0]   = INTENT_RELATIVE_COLORIMETRIC; Intents[1] = nIntent; Intents[2] = INTENT_RELATIVE_COLORIMETRIC; Intents[3] = INTENT_RELATIVE_COLORIMETRIC;
+
+    xform =  cmsCreateExtendedTransform(ContextID, 4, hProfiles, BPC, Intents,
+        States, NULL, 0, TYPE_Lab_DBL, TYPE_Lab_DBL, cmsFLAGS_NOCACHE|cmsFLAGS_NOOPTIMIZE);
+
+    cmsCloseProfile(ContextID, hLab);
+    return xform;
+}
+
+// Use darker colorants to obtain black point. This works in the relative colorimetric intent and
+// assumes more ink results in darker colors. No ink limit is assumed.
+static
+cmsBool  BlackPointAsDarkerColorant(cmsContext ContextID,
+                                    cmsHPROFILE hInput,
+                                    cmsUInt32Number Intent,
+                                    cmsCIEXYZ* BlackPoint,
+                                    cmsUInt32Number dwFlags)
+{
+    cmsUInt16Number *Black;
+    cmsHTRANSFORM xform;
+    cmsColorSpaceSignature Space;
+    cmsUInt32Number nChannels;
+    cmsUInt32Number dwFormat;
+    cmsHPROFILE hLab;
+    cmsCIELab  Lab;
+    cmsCIEXYZ  BlackXYZ;
+
+    // If the profile does not support input direction, assume Black point 0
+    if (!cmsIsIntentSupported(ContextID, hInput, Intent, LCMS_USED_AS_INPUT)) {
+
+        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+        return FALSE;
+    }
+
+    // Create a formatter which has n channels and no floating point
+    dwFormat = cmsFormatterForColorspaceOfProfile(ContextID, hInput, 2, FALSE);
+
+    // Try to get black by using black colorant
+    Space = cmsGetColorSpace(ContextID, hInput);
+
+    // This function returns darker colorant in 16 bits for several spaces
+    if (!_cmsEndPointsBySpace(Space, NULL, &Black, &nChannels)) {
+
+        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+        return FALSE;
+    }
+
+    if (nChannels != T_CHANNELS(dwFormat)) {
+       BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+       return FALSE;
+    }
+
+    // Lab will be used as the output space, but lab2 will avoid recursion
+    hLab = cmsCreateLab2Profile(ContextID, NULL);
+    if (hLab == NULL) {
+       BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+       return FALSE;
+    }
+
+    // Create the transform
+    xform = cmsCreateTransform(ContextID, hInput, dwFormat,
+                                hLab, TYPE_Lab_DBL, Intent, cmsFLAGS_NOOPTIMIZE|cmsFLAGS_NOCACHE);
+    cmsCloseProfile(ContextID, hLab);
+
+    if (xform == NULL) {
+
+        // Something went wrong. Get rid of open resources and return zero as black
+        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+        return FALSE;
+    }
+
+    // Convert black to Lab
+    cmsDoTransform(ContextID, xform, Black, &Lab, 1);
+
+    // Force it to be neutral, check for inconsistencies
+    if (Lab.L > 95)
+        Lab.L = 0; // Synthetic negative profiles
+    else if (Lab.L > 50)
+        Lab.L = 50;
+    else if (Lab.L < 0)
+        Lab.L = 0;
+    Lab.a = Lab.b = 0;
+
+    // Free the resources
+    cmsDeleteTransform(ContextID, xform);
+
+    // Convert from Lab (which is now clipped) to XYZ.
+    cmsLab2XYZ(ContextID, NULL, &BlackXYZ, &Lab);
+
+    if (BlackPoint != NULL)
+        *BlackPoint = BlackXYZ;
+
+    return TRUE;
+
+    cmsUNUSED_PARAMETER(dwFlags);
+}
+
+// Get a black point of output CMYK profile, discounting any ink-limiting embedded
+// in the profile. For doing that, we use perceptual intent in input direction:
+// Lab (0, 0, 0) -> [Perceptual] Profile -> CMYK -> [Rel. colorimetric] Profile -> Lab
+static
+cmsBool BlackPointUsingPerceptualBlack(cmsContext ContextID, cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile)
+{
+    cmsHTRANSFORM hRoundTrip;
+    cmsCIELab LabIn, LabOut;
+    cmsCIEXYZ  BlackXYZ;
+
+     // Is the intent supported by the profile?
+    if (!cmsIsIntentSupported(ContextID, hProfile, INTENT_PERCEPTUAL, LCMS_USED_AS_INPUT)) {
+
+        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+        return TRUE;
+    }
+
+    hRoundTrip = CreateRoundtripXForm(ContextID, hProfile, INTENT_PERCEPTUAL);
+    if (hRoundTrip == NULL) {
+        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+        return FALSE;
+    }
+
+    LabIn.L = LabIn.a = LabIn.b = 0;
+    cmsDoTransform(ContextID, hRoundTrip, &LabIn, &LabOut, 1);
+
+    // Clip Lab to reasonable limits
+    if (LabOut.L > 50) LabOut.L = 50;
+    LabOut.a = LabOut.b = 0;
+
+    cmsDeleteTransform(ContextID, hRoundTrip);
+
+    // Convert it to XYZ
+    cmsLab2XYZ(ContextID, NULL, &BlackXYZ, &LabOut);
+
+    if (BlackPoint != NULL)
+        *BlackPoint = BlackXYZ;
+
+    return TRUE;
+}
+
+// This function shouldn't exist at all -- there is such quantity of broken
+// profiles on black point tag, that we must somehow fix chromaticity to
+// avoid huge tint when doing Black point compensation. This function does
+// just that. There is a special flag for using black point tag, but turned
+// off by default because it is bogus on most profiles. The detection algorithm
+// involves to turn BP to neutral and to use only L component.
+cmsBool CMSEXPORT cmsDetectBlackPoint(cmsContext ContextID, cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile, cmsUInt32Number Intent, cmsUInt32Number dwFlags)
+{
+    cmsProfileClassSignature devClass;
+
+    // Make sure the device class is adequate
+    devClass = cmsGetDeviceClass(ContextID, hProfile);
+    if (devClass == cmsSigLinkClass ||
+        devClass == cmsSigAbstractClass ||
+        devClass == cmsSigNamedColorClass) {
+            BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+            return FALSE;
+    }
+
+    // Make sure intent is adequate
+    if (Intent != INTENT_PERCEPTUAL &&
+        Intent != INTENT_RELATIVE_COLORIMETRIC &&
+        Intent != INTENT_SATURATION) {
+            BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+            return FALSE;
+    }
+
+    // v4 + perceptual & saturation intents does have its own black point, and it is
+    // well specified enough to use it. Black point tag is deprecated in V4.
+    if ((cmsGetEncodedICCversion(ContextID, hProfile) >= 0x4000000) &&
+        (Intent == INTENT_PERCEPTUAL || Intent == INTENT_SATURATION)) {
+
+            // Matrix shaper share MRC & perceptual intents
+            if (cmsIsMatrixShaper(ContextID, hProfile))
+                return BlackPointAsDarkerColorant(ContextID, hProfile, INTENT_RELATIVE_COLORIMETRIC, BlackPoint, 0);
+
+            // Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents
+            BlackPoint -> X = cmsPERCEPTUAL_BLACK_X;
+            BlackPoint -> Y = cmsPERCEPTUAL_BLACK_Y;
+            BlackPoint -> Z = cmsPERCEPTUAL_BLACK_Z;
+
+            return TRUE;
+    }
+
+
+#ifdef CMS_USE_PROFILE_BLACK_POINT_TAG
+
+    // v2, v4 rel/abs colorimetric
+    if (cmsIsTag(ContextID, hProfile, cmsSigMediaBlackPointTag) &&
+        Intent == INTENT_RELATIVE_COLORIMETRIC) {
+
+            cmsCIEXYZ *BlackPtr, BlackXYZ, UntrustedBlackPoint, TrustedBlackPoint, MediaWhite;
+            cmsCIELab Lab;
+
+            // If black point is specified, then use it,
+
+            BlackPtr = cmsReadTag(ContextID, hProfile, cmsSigMediaBlackPointTag);
+            if (BlackPtr != NULL) {
+
+                BlackXYZ = *BlackPtr;
+                _cmsReadMediaWhitePoint(ContextID, &MediaWhite, hProfile);
+
+                // Black point is absolute XYZ, so adapt to D50 to get PCS value
+                cmsAdaptToIlluminant(ContextID, &UntrustedBlackPoint, &MediaWhite, cmsD50_XYZ(ContextID), &BlackXYZ);
+
+                // Force a=b=0 to get rid of any chroma
+                cmsXYZ2Lab(ContextID, NULL, &Lab, &UntrustedBlackPoint);
+                Lab.a = Lab.b = 0;
+                if (Lab.L > 50) Lab.L = 50; // Clip to L* <= 50
+                cmsLab2XYZ(ContextID, NULL, &TrustedBlackPoint, &Lab);
+
+                if (BlackPoint != NULL)
+                    *BlackPoint = TrustedBlackPoint;
+
+                return TRUE;
+            }
+    }
+#endif
+
+    // That is about v2 profiles.
+
+    // If output profile, discount ink-limiting and that's all
+    if (Intent == INTENT_RELATIVE_COLORIMETRIC &&
+        (cmsGetDeviceClass(ContextID, hProfile) == cmsSigOutputClass) &&
+        (cmsGetColorSpace(ContextID, hProfile)  == cmsSigCmykData))
+        return BlackPointUsingPerceptualBlack(ContextID, BlackPoint, hProfile);
+
+    // Nope, compute BP using current intent.
+    return BlackPointAsDarkerColorant(ContextID, hProfile, Intent, BlackPoint, dwFlags);
+}
+
+
+
+// ---------------------------------------------------------------------------------------------------------
+
+// Least Squares Fit of a Quadratic Curve to Data
+// http://www.personal.psu.edu/jhm/f90/lectures/lsq2.html
+
+static
+cmsFloat64Number RootOfLeastSquaresFitQuadraticCurve(cmsContext ContextID, int n, cmsFloat64Number x[], cmsFloat64Number y[])
+{
+    double sum_x = 0, sum_x2 = 0, sum_x3 = 0, sum_x4 = 0;
+    double sum_y = 0, sum_yx = 0, sum_yx2 = 0;
+    double d, a, b, c;
+    int i;
+    cmsMAT3 m;
+    cmsVEC3 v, res;
+
+    if (n < 4) return 0;
+
+    for (i=0; i < n; i++) {
+
+        double xn = x[i];
+        double yn = y[i];
+
+        sum_x  += xn;
+        sum_x2 += xn*xn;
+        sum_x3 += xn*xn*xn;
+        sum_x4 += xn*xn*xn*xn;
+
+        sum_y += yn;
+        sum_yx += yn*xn;
+        sum_yx2 += yn*xn*xn;
+    }
+
+    _cmsVEC3init(ContextID, &m.v[0], n,      sum_x,  sum_x2);
+    _cmsVEC3init(ContextID, &m.v[1], sum_x,  sum_x2, sum_x3);
+    _cmsVEC3init(ContextID, &m.v[2], sum_x2, sum_x3, sum_x4);
+
+    _cmsVEC3init(ContextID, &v, sum_y, sum_yx, sum_yx2);
+
+    if (!_cmsMAT3solve(ContextID, &res, &m, &v)) return 0;
+
+
+    a = res.n[2];
+    b = res.n[1];
+    c = res.n[0];
+
+    if (fabs(a) < 1.0E-10) {
+
+        if (fabs(b) < 1.0E-10) return 0;
+        return cmsmin(0, cmsmax(50, -c/b ));
+    }
+    else {
+
+         d = b*b - 4.0 * a * c;
+         if (d <= 0) {
+             return 0;
+         }
+         else {
+
+             double rt;
+
+             if (fabs(a) < 1.0E-10) return 0;
+
+             rt = (-b + sqrt(d)) / (2.0 * a);
+
+             return cmsmax(0, cmsmin(50, rt));
+         }
+   }
+
+}
+
+
+
+// Calculates the black point of a destination profile.
+// This algorithm comes from the Adobe paper disclosing its black point compensation method.
+cmsBool CMSEXPORT cmsDetectDestinationBlackPoint(cmsContext ContextID, cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile, cmsUInt32Number Intent, cmsUInt32Number dwFlags)
+{
+    cmsColorSpaceSignature ColorSpace;
+    cmsHTRANSFORM hRoundTrip = NULL;
+    cmsCIELab InitialLab, destLab, Lab;
+    cmsFloat64Number inRamp[256], outRamp[256];
+    cmsFloat64Number MinL, MaxL;
+    cmsBool NearlyStraightMidrange = TRUE;
+    cmsFloat64Number yRamp[256];
+    cmsFloat64Number x[256], y[256];
+    cmsFloat64Number lo, hi;
+    int n, l;
+    cmsProfileClassSignature devClass;
+
+    // Make sure the device class is adequate
+    devClass = cmsGetDeviceClass(ContextID, hProfile);
+    if (devClass == cmsSigLinkClass ||
+        devClass == cmsSigAbstractClass ||
+        devClass == cmsSigNamedColorClass) {
+            BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+            return FALSE;
+    }
+
+    // Make sure intent is adequate
+    if (Intent != INTENT_PERCEPTUAL &&
+        Intent != INTENT_RELATIVE_COLORIMETRIC &&
+        Intent != INTENT_SATURATION) {
+            BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+            return FALSE;
+    }
+
+
+    // v4 + perceptual & saturation intents does have its own black point, and it is
+    // well specified enough to use it. Black point tag is deprecated in V4.
+    if ((cmsGetEncodedICCversion(ContextID, hProfile) >= 0x4000000) &&
+        (Intent == INTENT_PERCEPTUAL || Intent == INTENT_SATURATION)) {
+
+            // Matrix shaper share MRC & perceptual intents
+            if (cmsIsMatrixShaper(ContextID, hProfile))
+                return BlackPointAsDarkerColorant(ContextID, hProfile, INTENT_RELATIVE_COLORIMETRIC, BlackPoint, 0);
+
+            // Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents
+            BlackPoint -> X = cmsPERCEPTUAL_BLACK_X;
+            BlackPoint -> Y = cmsPERCEPTUAL_BLACK_Y;
+            BlackPoint -> Z = cmsPERCEPTUAL_BLACK_Z;
+            return TRUE;
+    }
+
+
+    // Check if the profile is lut based and gray, rgb or cmyk (7.2 in Adobe's document)
+    ColorSpace = cmsGetColorSpace(ContextID, hProfile);
+    if (!cmsIsCLUT(ContextID, hProfile, Intent, LCMS_USED_AS_OUTPUT ) ||
+        (ColorSpace != cmsSigGrayData &&
+         ColorSpace != cmsSigRgbData  &&
+         ColorSpace != cmsSigCmykData)) {
+
+        // In this case, handle as input case
+        return cmsDetectBlackPoint(ContextID, BlackPoint, hProfile, Intent, dwFlags);
+    }
+
+    // It is one of the valid cases!, use Adobe algorithm
+
+
+    // Set a first guess, that should work on good profiles.
+    if (Intent == INTENT_RELATIVE_COLORIMETRIC) {
+
+        cmsCIEXYZ IniXYZ;
+
+        // calculate initial Lab as source black point
+        if (!cmsDetectBlackPoint(ContextID, &IniXYZ, hProfile, Intent, dwFlags)) {
+            return FALSE;
+        }
+
+        // convert the XYZ to lab
+        cmsXYZ2Lab(ContextID, NULL, &InitialLab, &IniXYZ);
+
+    } else {
+
+        // set the initial Lab to zero, that should be the black point for perceptual and saturation
+        InitialLab.L = 0;
+        InitialLab.a = 0;
+        InitialLab.b = 0;
+    }
+
+
+    // Step 2
+    // ======
+
+    // Create a roundtrip. Define a Transform BT for all x in L*a*b*
+    hRoundTrip = CreateRoundtripXForm(ContextID, hProfile, Intent);
+    if (hRoundTrip == NULL)  return FALSE;
+
+    // Compute ramps
+
+    for (l=0; l < 256; l++) {
+
+        Lab.L = (cmsFloat64Number) (l * 100.0) / 255.0;
+        Lab.a = cmsmin(50, cmsmax(-50, InitialLab.a));
+        Lab.b = cmsmin(50, cmsmax(-50, InitialLab.b));
+
+        cmsDoTransform(ContextID, hRoundTrip, &Lab, &destLab, 1);
+
+        inRamp[l]  = Lab.L;
+        outRamp[l] = destLab.L;
+    }
+
+    // Make monotonic
+    for (l = 254; l > 0; --l) {
+        outRamp[l] = cmsmin(outRamp[l], outRamp[l+1]);
+    }
+
+    // Check
+    if (! (outRamp[0] < outRamp[255])) {
+
+        cmsDeleteTransform(ContextID, hRoundTrip);
+        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+        return FALSE;
+    }
+
+
+    // Test for mid range straight (only on relative colorimetric)
+    NearlyStraightMidrange = TRUE;
+    MinL = outRamp[0]; MaxL = outRamp[255];
+    if (Intent == INTENT_RELATIVE_COLORIMETRIC) {
+
+        for (l=0; l < 256; l++) {
+
+            if (! ((inRamp[l] <= MinL + 0.2 * (MaxL - MinL) ) ||
+                (fabs(inRamp[l] - outRamp[l]) < 4.0 )))
+                NearlyStraightMidrange = FALSE;
+        }
+
+        // If the mid range is straight (as determined above) then the
+        // DestinationBlackPoint shall be the same as initialLab.
+        // Otherwise, the DestinationBlackPoint shall be determined
+        // using curve fitting.
+        if (NearlyStraightMidrange) {
+
+            cmsLab2XYZ(ContextID, NULL, BlackPoint, &InitialLab);
+            cmsDeleteTransform(ContextID, hRoundTrip);
+            return TRUE;
+        }
+    }
+
+
+    // curve fitting: The round-trip curve normally looks like a nearly constant section at the black point,
+    // with a corner and a nearly straight line to the white point.
+    for (l=0; l < 256; l++) {
+
+        yRamp[l] = (outRamp[l] - MinL) / (MaxL - MinL);
+    }
+
+    // find the black point using the least squares error quadratic curve fitting
+    if (Intent == INTENT_RELATIVE_COLORIMETRIC) {
+        lo = 0.1;
+        hi = 0.5;
+    }
+    else {
+
+        // Perceptual and saturation
+        lo = 0.03;
+        hi = 0.25;
+    }
+
+    // Capture shadow points for the fitting.
+    n = 0;
+    for (l=0; l < 256; l++) {
+
+        cmsFloat64Number ff = yRamp[l];
+
+        if (ff >= lo && ff < hi) {
+            x[n] = inRamp[l];
+            y[n] = yRamp[l];
+            n++;
+        }
+    }
+
+
+    // No suitable points
+    if (n < 3 ) {
+        cmsDeleteTransform(ContextID, hRoundTrip);
+        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+        return FALSE;
+    }
+
+
+    // fit and get the vertex of quadratic curve
+    Lab.L = RootOfLeastSquaresFitQuadraticCurve(ContextID, n, x, y);
+
+    if (Lab.L < 0.0) { // clip to zero L* if the vertex is negative
+        Lab.L = 0;
+    }
+
+    Lab.a = InitialLab.a;
+    Lab.b = InitialLab.b;
+
+    cmsLab2XYZ(ContextID, NULL, BlackPoint, &Lab);
+
+    cmsDeleteTransform(ContextID, hRoundTrip);
+    return TRUE;
+}